Overshot



Aug. 23, 1938. R. P. SHERMAN OVERSHO? Filed June 22. 1956 Fig. 4

Ralph P. Sherman INVENTOR a Mb W3 M/.5

Patented Aug. 23, 1938 OVERSHOT Ralph P. Sherman, Houston, Tex.,asslgnor to Hughes Tool Company, Houston, Tex a corporation oi! TexasApplication June 22, 1936, SerialNo. 88,514

8 Claims.

My invention relates to overshots for engagement with devices positionedin the bore of a well. It is adapted particularly to engage tools in thewell to withdraw them, where such tools are provided with means to beengaged by said overshot. My invention is not confined to use in suchsituations, however, as will appear from the description which follows.

It is an object of the invention to provide an overshot which isreleasable from the object engaged by it if the object is stuck andcannot be moved. a

I desire to provide, in connection with the gripping means, a frangibletension means which will break under a predetermined strain and. releasethe tool.

It is a further object of the invention to provide means whereby thetool withdrawn by the overshot may be easily disengaged from theovershot when the tool has been withdrawn from the well.

It is a further object to provide an overshot which is easily engagedwith the tool to be withdrawn but which will not release the tool if itis possible to pull the same. The invention also includes the particularstructure of the releasing mechanism which will release the tool with aminimum of effort when it has been withdrawn.

In the drawing herewith Fig. 1 is a central longitudinal section throughan overshot embodying my invention.

Fig. 2 is a broken longitudinal section showin the releasing device in aposition different from' that indicated in Fig. 1.

Fig. 3 is a, transverse section on the plane 3-4 of Fig. l,somewhatenlarged.

Fig. 4 is a similar enlarged transverse section on the plane 44 of Fig.1.

The body of my overshot includes a tubular barrel or housing I the lowerend of which has threaded thereto a cap 2. Said cap has an axial opening4 and the wall about said opening is tapered upwardly at 3 to provide anouter cam surface which serves to spread the jaws 5 of the grippingdevices, as will be later noted. There are fluid conducting openings 6through the end of said cap.

The inner walls of the housing 'I are recessed to cooperate with thejaws 5 which are mounted on an inverted U-shaped spring I the upper loopof which is engaged about a transverse pin 8 in a supporting block 9fitting slidably within the housing. Said dogs are secured to the armsof spring I by rivets ID or by equivalent means and their lower endshave inwardly projecting shoulders presented upwardly to engage belowthe head I2 oi.- a tool in the well. Below said shoulders the innerfaces of said dogs are flared downwardly to engage the projection 3 onthe cap 2. One of the spring arms has its lower end bent inwardly toform a stop 13 to be engaged by the head l2 and limit the relativedownward movement of the overshot over said head l2. The outer faces ofthe dogs at their lower ends are enlarged to engage the inner wall ofthe' housing. Above the normal position of the dogs, as seen in Fig. 1,the inner wall of the housing is recessed at M to allow said dogs tomove outwardly. The interior is also recessed at l5 below the dogs toalso allow separation of the dogs when they are moved downwardly fromnormal position.

The block 9 upon which the supporting spring is engaged has its upperend formed to receive the lower head It of a tension link l1. Said headI6 is slidable laterally in a slot l8 into an axial position in. saidblock. The head l6 moves in an undercut recess l9 and is latched inaxial position by a ball 20 engaging in a lower recess in the head It.Said ball is held resiliently upwardly by a spring 2| resting upon aremovable plug 22 in the block.

The tension link II has a head Ifia at its upper end adapted to beengaged by the lower ends of a pair of dogs 23. Said dogs are hinged attheir upper ends to a transverse pin 24, the outer reduced ends 25 ofwhich are movable 111 slots 26 in the wall of the housing. There is asleeve bushing 21 on the shaft, as will be noted from Fig. 3, upon whichthe dogs are mounted. A spring 28 on said bushing engages said dogs andtends to move the lower ends outwardly against the inner wall of thehousing.

Adjacent the lower ends of the dogs the inner I wall of the housing istapered inwardly and downwardly at 29 to be contacted by the beveledlower ends of said dogs, and hold them inwardly engaging about the headl6a of the tension link I! and hold the link firmly supported.

The upper end of housing I is reduced in diameter and a locking sleeve30 is fitted thereon. Above the sleeve is a cap or nipple 3| whichcloses 4 the end of the housing and has a threaded shank 32 to couplewith the operating string which may include a wire cable.

The sleeve 30 has its lower end cut away on opposite sides thus formingtwo opposite cam surfaces 33 to cooperate to move the pin 24 in the slot26. The sleeve has a pair of opposite openings 34 therein and a pair oflarger openings 35 thereinspaced 90 from the smaller openings.

,A latch bolt 36 is housed within a transverse opening in a block 31fitting within the upper end ing pin 38. Said bolt is recessed atone endto receive a compression spring 39 which tends to holdsaid bolt 36radially outwardly to engage within one of the openings 34 and 35 in thesleeve 30. The outer latching end of the bolt has a small diameter 40toengage the openings 34 and a larger diameter 4| to engage the largeropening 35. It will be seen that, when latched in the smaller opening 34as shown in Fig. 1, the lower cam surface of the sleeve will hold thepin 24 of the latching mechanism downwardly. When the larger diameter 4iengages in one of the openings 35, the sleeve 30 will permit theupwardmovement of the pin 24 in the slot 26.

When this overshot is employed to remove from within the drill stem atool, such as a re-. tractible core barrel, for example, the overshot islowered atthe end of a wire line. When thus lowered the ports are set asshown in Fig. 1.

the knob 12 thereon will pass upwardly through the opening 4 in theovershot and by engaging the lower ends of dogs 5, will move themupwardly into the recess l4 where said dogs will be spread apart andwhen the knob I2 is in position against the stop I3 the dogs will snapinwardly below the same and an upward pull on the overshot will move thedogs downwardly to locked position, as shown.

An upward pull on the overshot will lift the core barrel.

If the core barrel should be lodged too tightly so that it could not bepulled, the stem of the tension link I! will break, when a certainpredetermined tension has been exceeded, and allow the dogs to drop intothe recess l where the projection 3 will spread the dogs apart andrelease the knob II. The overshot may then be withdrawn from the drillpipe.

If the core barrel can be withdrawn the overshot must then be disengagedfrom the knob H of the barrel. To do this the dogs 5 which hold the knobl2 must be moved down from looking position as seen in Fig. 1. To dothis, I unlatch the upper end of the tension link from the holding dogs23. A rod or tool will be used to shove the bolt 36 inwardly so thatsleeve 30 may be rotated through 90 and thus allow the pin 24 to moveupwardly in the slot 26. The bolt 36 will then latch in opening 35 asseen in Fig. 2. The tension of spring 28 will tend to urge the dogsoutwardly so that, when the dogs have been moved upwardly along thetapered surface 29, they will release the head Hill of the tension link.This upward movement of the link I! is accomplished by shoving the tooland knob I 2 upwardly relative to the overshot; the supporting block 9being thereby moved to the position shown in Fig. '2. The link I! isthereby released and the block 9 and dogs 5 will drop down so as torelease the knob ii. on the core barrel. The overshot could then bereset for further use.

The tension link I! is arranged so that it may be examined to determinewhether it has been stretched or cracked. An opening 43 is slottedin theside of the housing I adjacent said link so as to provide a clear viewof said link for observation and replacement.

My overshot has the advantage of being easily engaged and disengagedfrom the tool which is to be removed. Also it is releasable by thebreaking of the link under strain too great for the tool to withstand.After the device has been withdrawn, it is quickly released from thecore barrel by simply unlatching and rotating the sleeve 30 and thencollapsing the overshot toward the core barrel as described.

What I claim as new is:

1. In an overshot, a tubular housing, tool gripping dogs enclosed withinthe lower end of said housing, means to support said dogs in saidhousing in position with said dogs latched on said tool, said meansbeing rendered ineii'ective to retain said dogs in latched position inresponse to a predetermined pulling force applied thereto and wedgingmeans in said housing below said dogs to unlatch said dogs when they aremoved from latched position.

2. In an overshot, a tubular housing, tool gripaping dogs enclosedwithin said housing, said dogs being held together in gripping positionby the wall of said housing, said wall being recessed above and belowthe said gripping position, means to support said dogs in grippingposition but allowing a limited upward movement thereof, said supportingmeans being rendered inefiective to support said dogs in response to apredetermined strain exerted thereon.

3. In an overshot, a tubular housing, tool gripping dogs enclosed withinsaid housing, said dogs being held together in gripping position by the,wall of said housing, said wall being recessed above and below the saidgripping position, means to support said dogs in gripping position, saidsupporting means being rendered inefiective to support said dogs inresponse to a predetermined strain exerted thereon.

4. In an overshot, a tubular housing, tool gripping clogs enclosedwithin said housing, said dogs being held together in gripping positionby the wall of said housing, said wall being. recessed above and belowthe said gripping position, means to support said dogs in grippingposition but allowing a limited upward movement thereof, said supportingmeans being of frangible material adapted to break under a predeterminedstrain to allow the said dogs to drop downward into releasing position.

5. In an overshot, a tubular housing, tool gripping dogs enclosed withinsaid housing, said dogs being held together in gripping position by thewall of said housing, said wall being recessed above and below the saidgripping position, means to support said dogs in gripping position butallowing a limited upward movement thereof, said supporting means beingof frangible material adapted to break under a predetermined strain toallow the said dogs to drop downward into releasing position and meansto then spread said dogs apart to release the tool.

6. An overshot includinga tubular housing, tool gripping dogs therein,means to support said dogs in tool gripping position, detachable meansin said housing to latch said supporting means against movement totool-releasing position in said housing, means to release said latchingmeans, said latching means operated responsive to an upward thrust onthe tool gripping dogs to move to open position.

7. In an overshot, a tubular housing, tool engaging dogs therein, meansto support said dogs in tool-engaging position including a frangiblelink, means to grip and hold the upper end of said link, releasable onthe upward movement of said gripping means in said housing, means toprevent the upward movement of said gripping means releasable manuallywhen desired to allow said link and dogs to move downward to disensaidhousinl. a pin to which said :laws are congage said dogs from said tool.nected, a sleeve on said houainc adapted tov en- 8. In an overshot, atubular housing, tool engaze and hold said pin and don: downwardlygaging dogs therein, means to support said dogs when said sleeve is inone position, but adapted in tool-engaging position including afrangible to release said pin and don: when said sleeve is 5 link, meansto grip and hold the upper end of rotated to another position.

said link, including a pair of link engaging jaws fitting within adownwardly tapered recess in Bil-PH P. SHERMAN.

